References of "Weber, M. H."
     in
Bookmark and Share    
Full Text
Peer Reviewed
See detailDead sea basin imaged by ambient seismic noise tomography
Stankiewicz, Jacek UL; Weber, M. H.; Mohsen, A. et al

in Pure and Applied Geophysics (2012), 169(4), 615-623

Detailed reference viewed: 14 (0 UL)
Full Text
Peer Reviewed
See detailDeep crustal seismic reflection experiment across the southern Karoo Basin, South Africa
Lindeque, A. S.; Ryberg, T.; Stankiewicz, Jacek UL et al

in South African Journal of Geology (2007), 110(2-3), 419-438

A controlled source Near Vertical Reflection (NVR) Seismic experiment along a ~100 km profile yields the first high quality seismic image of the crust and Moho across the southern Karoo Basin in South ... [more ▼]

A controlled source Near Vertical Reflection (NVR) Seismic experiment along a ~100 km profile yields the first high quality seismic image of the crust and Moho across the southern Karoo Basin in South Africa. The highly reflective crust comprises upper, middle and lower layers. In the upper crust, folded and gently south-dipping continuous reflectors up to the Escarpment, represent the bedding of the Karoo and Cape Supergroups respectively. Décollement structures occur locally along carbonaceous shales of the Whitehill Formation. A well-defined mid-crustal layer that hosts the Beattie Magnetic Anomaly (BMA), occurs below a seismically imaged unconformity. The mid-crustal layer is ~20 km thick in the vicinity of the BMA and is likely to be a subsurface continuation of the 1.0 to 2.0 Ga granitoid gneisses of the Bushmanland sub-province in the 1.2 to 1.0 Ga Namaqua-Natal Orogenic Belt. The internal seismic fabric of this layer is interpreted as a tectonic fabric dipping to the north. The probable source of the BMA appears at 7 to 15 km depth, as a narrow feature in a ~10 km wide tectonically complex zone confined to the upper midcrust. The underlying lower crustal layer is wedge-shaped: ~24 km thick in the north and decreasing to ~12 km thick beneath the Cape Fold Belt. This lower crustal layer may represent granulite-gneisses of the Namaqua sub-province. The internal seismic fabric in the upper part of this layer dips both to the north and south, but a north-dipping fabric dominates the lower part. A clearly imaged undulating Moho occurs at a depth of ~43 km in the north, with a nick point at ~42 km depth, ~35 km along the profile, and then deepens to ~45 km in the south beneath the tectonic front of the Cape Fold Belt. A possible ~1 to 2 km thick lowermost crustal layer of high seismic reflectivity, overlies the Moho and may represent underplated mafic material. The reflectivity seen in this NVR seismic image bears similarities to seismic transects across the coeval Mesoproterozoic Grenville orogen in Canada [less ▲]

Detailed reference viewed: 52 (0 UL)
Full Text
Peer Reviewed
See detailInitial results from wide-angle seismic refraction lines in the southern Cape
Stankiewicz, Jacek UL; Ryberg, T.; Schulze, A. et al

in South African Journal of Geology (2007), 110(2-3), 407-418

One of the projects within the framework of Inkaba yeAfrica, an earth system science initiative between German and South African research communities, is the Agulhas-Karoo transect. This 800 km north ... [more ▼]

One of the projects within the framework of Inkaba yeAfrica, an earth system science initiative between German and South African research communities, is the Agulhas-Karoo transect. This 800 km north-south off-onshore transect runs from the offshore Agulhas Plateau onto the South African coast, across the Cape Fold Belt, Beattie Magnetic Anomaly, the Karoo Basin, the Great Escarpment and into the Kaapvaal Craton. Among the number of geophysical measurements taken along the transect are two wide-angle on-shore seismic lines collected in April and May 2005. The lines run roughly parallel to each other approximately 200 km apart, starting at Mossel Bay and St. Francis, and running about 200 km north to Fraserburg and Graaf Reinet, respectively. At each line 48 seismic receivers were used to record data from 13 shots. The profiles cross a wide variety of geological terrains, such as the siliciclastic sequences of the Paleozoic – Mesozoic Karoo and Oudtshoorn basins, the lower Paleozoic Cape Fold Belt, and the Eocambrian Kango and Kaaimans inliers. They also cross the Beattie Magnetic Anomaly, a large east-west orientated crustal feature within the upper crust, and more than 1000 km long, first reported almost a century ago, but still not fully understood. The overall quality of seismic data is very good. First (P-wave) arrivals were manually picked on the available traces, and tomographic inversion was done using these travel times. The ray coverage made it possible to create the P-wave velocity model to depths of up to 25 km. We find excellent correlation of the shallow features with surface rock type. Deeper down we can identify both stratigraphic and tectonic contacts between geological groups. These include an inferred possible blind Paleozoic thrust fault, and the unconformity between the Cape Supergroup and the Namaqua-Natal Metamorphic Complex. The normal listric geometry of the Kango and Gamtoos Faults is clearly seen to a minimum depth of 15 km. We also observe a high velocity anomaly within the NNMC at ~10 km depth that we relate to the source of the Beattie Magnetic Anomaly. [less ▲]

Detailed reference viewed: 16 (0 UL)